CN111167483A

CN111167483A - MoSe2Preparation method and application of/ZnCdS nano-particles

Info

Publication number: CN111167483A
Application number: CN202010039044.0A
Authority: CN
Inventors: 乔秀清; 贾艳琳; 王紫昭; 李秋昊
Original assignee: China Three Gorges University CTGU
Current assignee: China Three Gorges University CTGU
Priority date: 2020-01-14
Filing date: 2020-01-14
Publication date: 2020-05-19

Abstract

The invention relates to MoSe₂The preparation method of the ZnCdS nano-particles and the application of the ZnCdS nano-particles in photocatalytic hydrogen production have the advantages of small size and uniform dispersion. Belongs to the field of nano material preparation technology and energy development. Firstly, selenium powder, sodium molybdate and the like are taken as raw materials to synthesize MoSe by a hydrothermal method₂Then zinc acetate, cadmium acetate and other raw materials are used for synthesizing Zn_0.5Cd_0.5S nano particles are uniformly mixed and dried by an ultrasonic oscillation method to form MoSe₂a/ZnCdS composite material. The nano composite material shows excellent catalytic activity in photocatalytic hydrogen production.

Description

MoSe2Preparation method and application of/ZnCdS nano-particles

Technical Field

The invention belongs to the field of nano material preparation technology and green energy, and particularly relates to MoSe₂A preparation method of a/ZnCdS composite material and application thereof in photocatalytic hydrogen production.

Background

With the development of human beings, environmental and energy problems are two problems faced at present. Excessive exploitation of fossil energy and environmental degradation compel the search for a sustainable, environmentally friendly energyA source. Hydrogen is considered an ideal energy carrier and has a chemical bond with H₂O as the only oxidation product is environmentally friendly. In recent years, H separated by photocatalytic water₂Evolution has achieved significant success. It is still a challenging task to rationally design a photocatalyst that is continuously and efficiently responsive to visible light. Bimetallic sulfide Cd_0.5Zn_0.5S is taken as a typical noble metal-free macromolecular semiconductor photocatalyst, has good environmental friendliness, good physical and chemical stability and unique photoelectronic characteristics, but has low surface area, and the catalytic activity is directly reduced due to factors such as low electron hole separation efficiency, weak charge carrier migration capability and the like in the photocatalytic reaction process. Cd [ Cd ]_0.5Zn_0.5The photocatalytic activity of the S photocatalyst is far from meeting the basic requirements of practical application. In conventional photocatalytic systems, the promoter not only aids in electron-hole separation at the promoter-semiconductor interface, but is also H₂The evolution provides the active site. MoSe₂Has good diffusion active center and metal electron conductivity in a photocatalytic system. Therefore, we use MoSe₂As cocatalyst, Cd_0.5Zn_0.5S is a main catalyst to construct MoSe₂The composite material of the/ZnCdS and the H can be compounded₂The evolution of (2) provides abundant active sites and can increase photo-generated charge transfer, thereby reducing the carrier recombination probability. Thereby improving photocatalytic performance.

Disclosure of Invention

Aiming at the technical problem, the invention prepares the MoSe₂The introduction of the cocatalyst of the ZnCdS composite material provides more active centers and effective charge transfer, so that the catalytic activity of the composite material is obviously improved.

Zn is used as the main component of the invention_0.5Cd_0.5S nano-particles are used as a main catalyst and MoSe₂The nano-sheet is taken as a cocatalyst to form MoSe₂ZnCdS nanocomposite.

Wherein, MoSe₂As a two-dimensional layered nano material, has good expansion in a photocatalytic systemA scattered active center and metal electron conductivity. The ZnCdS solid solution shows strong catalytic activity on water cracking hydrogen production under the irradiation of visible light, and has higher chemical stability. But the original ZnCdS active site has poor dispersion, low electron hole separation efficiency, weak light-excited charge carrier migration capability and the like. Thus, MoSe was introduced₂The defects of low specific surface area and rapid recombination of photoinduced charge carriers existing in ZnCdS are overcome. The invention uses MoSe₂Which complexes with the bimetallic sulfide to better separate the charge and activate the reactant.

In order to achieve the purpose, the invention adopts the technical scheme that:

firstly, selenium powder, sodium molybdate and the like are taken as raw materials to synthesize MoSe by a hydrothermal method₂Then zinc acetate, cadmium acetate and other raw materials are used for synthesizing Zn_0.5Cd_0.5S nano particles are uniformly mixed and dried by an ultrasonic oscillation method to form MoSe₂a/ZnCdS composite material. When MoSe₂When the adding amount is 9 wt%, the nano composite material shows excellent catalytic activity in photocatalytic hydrogen production.

The MoSe of the invention₂The preparation method of the/ZnCdS composite material comprises the following steps:

1) zn (Ac)₂·2H₂O、Cd(Ac)₂·2H₂O and thioacetamide were dissolved in 40mL of distilled water. An aqueous NaOH solution was then added to the above solution under strong stirring until a homogeneous solution was formed. The solution was transferred to a teflon lined autoclave and the autoclave was sealed and held in an oven at 160-200 ℃ for 20-24 hours. After the autoclave was naturally cooled at room temperature, the resulting yellow product was collected, centrifuged several times with water and ethanol, and dried at 60 ℃ for 8 hours. In the preferred embodiment, Zn is obtained_0.5Cd_0.5And (3) S solid solution.

Said Zn (Ac)₂·2H₂O、Cd(Ac)₂·2H₂The molar ratio of O to thioacetamide is 1:0.8-1.2: 1.8-3.0.

2) Reacting NaBH₄Se powder and sodium molybdate are dissolved in deionized water and stirred uniformly, and the uniform solution is transferred to a lining made of polytetrafluoroethyleneHeating in water at 160-200 deg.C for 18-24 hr in high pressure kettle, centrifuging to collect black precipitate, washing with deionized water and anhydrous ethanol for three times, and drying at 60 deg.C to obtain MoSe₂Nanosheets.

The NaBH₄The mass ratio of the Se powder to the sodium molybdate is 1:0.8-1.2: 1.3-2.

3) Adding ethanol into a centrifugal tube, and adding the prepared ZnCdS nano-particles (1) and the prepared MoSe (2)₂Adding the powder into ethanol, performing ultrasonic treatment for 30min to form a uniform solution, and evaporating ethanol at 100 ℃ to obtain the target MoSe₂ZnCdS nanocomposite.

The ZnCdS nano-particles and MoSe₂The mass ratio of the nano-sheets is 88-97: 3-12.

The invention also provides a method for synthesizing MoSe₂The application of the/ZnCdS composite material in photocatalytic hydrogen production.

The method comprises the following specific steps: under the irradiation of visible light, hydrogen production reaction is carried out in a closed quartz reaction system, the temperature of the reaction system is kept between 5 and 8 ℃ by cooling circulating water, and MoSe is added₂the/ZnCdS nanomaterial was dispersed in 80 mL lactic acid and deionized water solution (8 mL lactic acid, 72 mL water) and completely degassed under continuous stirring, and analyzed for hydrogen evolution using an online gas chromatography (FULI, GC-7920) with a 300W Xe arc lamp with a 420 nm filter (CEL-HXF300) as the light source, showing MoSe₂the/ZnCdS nano material has excellent photocatalytic hydrogen production activity.

The invention provides a novel composite material for photocatalytic hydrogen production and a preparation method thereof, and the novel composite material is applied to photocatalytic hydrogen production, and has the advantages of reasonable and simple preparation method, obvious improvement on hydrogen production performance and excellent photocatalytic hydrogen production activity.

The invention adopts a simple solvothermal method and an ultrasonic mixing method to synthesize MoSe₂The ZnCdS nano material has good conductivity and more active sites, and the synthesized composite material has excellent hydrogen production performance under visible light, and can be widely applied to the field of green energy.

The reaction mechanism is as follows: MoSe prepared by the patent₂ZnCdS sodiumThe rice material shows excellent catalytic activity in photocatalytic hydrogen production, mainly due to MoSe₂And ZnCdS form a heterostructure, namely in the illumination reaction process, both a conduction band and a valence band of the ZnCdS generate electrons and holes, and due to the interaction of the electrons and the matched energy band potential, light-excited electrons are rapidly transferred from the ZnCdS to MoSe₂A cocatalyst. At the same time, the photogenerated holes in the ZnCdS valence band can be consumed by the sacrificial agent (lactic acid). Namely, the remarkable improvement of the photocatalytic activity in the illumination reaction process can be attributed to ZnCdS and MoSe₂Efficient separation and transfer of charge at the interface and extension of the life of the photo-induced charge carriers.

Drawings

FIG. 1: zn prepared for example 1_0.5Cd_0.5S，MoSe₂，MoSe₂X-ray diffraction Pattern of/ZnCdS (Zn)_0.5Cd_0.5S is a ZnCdS sample; zn_0.5Cd_0.5S/3%MoSe₂Represents MoSe₂MoSe with the loading of 3 percent₂ZnCdS composite, others are the same).

FIG. 2: MoSe obtained for example 1₂Scanning electron microscope picture of/ZnCdS composite material (the left picture is MoSe)₂Scanning graph of/ZnCdS composite material, and the right graph is Zn_0.5Cd_0.5Scanning electron microscopy of S nanoparticles).

FIG. 3: MoSe obtained for example 1₂Absorption spectrum performance diagram of/ZnCdS composite material (ZCS represents pure Zn)_0.5Cd_0.5S sample, ZCS/6, 9, 12% MoSe₂Respectively represent MoSe₂MoSe with the loading amounts of 6%, 9% and 12%₂ZnCdS composite material, the same below).

FIG. 4: the catalyst ZnCdS, MoSe obtained in example 1₂Photoelectromogram of/ZnCdS composite (ZCS stands for pure Zn)_0.5Cd_0.5S sample, ZCS/9% MoSe₂、ZCS/12%MoSe₂Respectively represent MoSe₂MoSe with the loading capacity of 9 percent and 12 percent₂ZnCdS composite material, the same below).

FIG. 5: the catalyst ZnCdS, MoSe obtained in example 1₂，MoSe₂Alternating current of/ZnCdS composite materialImpedance diagram (ZCS stands for pure Zn)_0.5Cd_0.5S sample, ZCS/9% MoSe₂、ZCS/12%MoSe₂Respectively represent MoSe₂MoSe with the loading capacity of 9 percent and 12 percent₂ZnCdS composite material, the same below).

FIG. 6: is ZnCdS, MoSe of example 2₂Photocatalytic hydrogen production performance test of/ZnCdS composite material (ZCS represents pure Zn)_0.5Cd_0.5S sample, ZCS/3% MoSe₂、ZCS/6%MoSe₂、ZCS/9%MoSe₂、ZCS/12%MoSe₂Respectively represent MoSe₂MoSe with the loading capacity of 9 percent and 12 percent₂ZnCdS composite material, the same below).

Detailed Description

Example 1

1) Mixing 5mmol Zn (Ac)₂·2H₂O、5mmolCd(Ac)₂·2H₂O and 12.5mmol thioacetamide were dissolved in 40mL distilled water. Then 10mL of 4m naoh aqueous solution was added to the above solution under strong stirring until a homogeneous solution was formed. The solution was transferred to a teflon lined autoclave and the autoclave was sealed and held in an oven at 180 ℃ for 24 h. After the autoclave was naturally cooled at room temperature, the resulting yellow product was collected, centrifuged several times with water and ethanol, and dried in an oven at 60 ℃ for 8 hours. Obtained Zn_0.5Cd_0.5And (3) S solid solution.

2) 0.304 g of NaBH₄0.316 gSe powder and 0.57 g of sodium molybdate are dissolved in 75 mL of deionized water and are stirred uniformly, the uniform solution is transferred into an autoclave with polytetrafluoroethylene as a lining, the autoclave is hydrothermal for 20 hours at 180 ℃, black precipitates are collected by centrifugation, the mixture is washed with deionized water and absolute ethyl alcohol for three times respectively, and the mixture is dried at 60 ℃ to obtain MoSe₂Nanosheets.

3) Adding 5mL of ethanol into a 10mL centrifuge tube, and mixing the prepared ZnCdS nano-particles (1) and the prepared MoSe₂Adding the powder (the addition amount is 3%, 6%, 9% and 12% in the composite material by mass) into ethanol, performing ultrasonic treatment for 30min to form a uniform solution, and evaporating the ethanol at 100 ℃ to obtain the target MoSe₂ZnCdS nanocomposite.

Example 2

1) MoSe obtained in example 1₂the/ZnCdS composite material catalyst is used for photocatalytic hydrogen production by visible light.

The hydrogen production experiment was performed in a closed quartz reaction system under visible light irradiation, the temperature of the reaction system was maintained at 6 ℃ by cooling circulating water, 20 mg of the catalyst was dispersed in a solution of 80 mL of lactic acid and deionized water (8 mL of lactic acid, 72 mL of water) with lactic acid as a sacrificial agent, which was completely deaerated under continuous stirring, and hydrogen evolution analysis was performed by online gas chromatography (FULI, GC-7920) using a 300W Xe arc lamp with a 420 nm filter (CEL-HXF300) as a light source. After the start of the illumination, samples were taken every 1 hour to obtain the hydrogen production histogram shown in FIG. 6. Can obtain, MoSe₂MoSe when the adding amount is 9 percent₂The hydrogen yield of the/ZnCdS composite material is 4853.3 mu mol.h^-1·g^-1。

Claims

1. MoSe₂The preparation method of the/ZnCdS nano-particles is characterized by comprising the following steps of:

(1) preparation of ZnCdS nanoparticles by reacting Zn (Ac)₂·2H₂O、Cd(Ac)₂·2H₂Dissolving O and thioacetamide in distilled water, adding NaOH aqueous solution while stirring until a uniform solution is formed, sealing, carrying out hydrothermal reaction at 160-200 ℃ for 20-24 hours, naturally cooling to room temperature, collecting a product, and drying to obtain ZnCdS nanoparticles;

（2）MoSe₂preparation of nanosheets, NaBH₄Dissolving Se powder and sodium molybdate in deionized water, stirring uniformly, carrying out hydrothermal reaction at 160-200 ℃ for 18-24h, collecting the product, and drying to obtain MoSe₂Nanosheets;

(3) preparation of MoSe2/ZnCdS nanoparticles by adding ZnCdS nanoparticles and MoSe into ethanol₂Performing ultrasonic dispersion on the nanosheets, and evaporating ethanol at 90-100 ℃ to obtain a target product MoSe₂ZnCdS nanoparticles.

2. The MoSe of claim 1₂Preparation method of/ZnCdS nano-particlesThe method is characterized in that in the step (1), Zn (Ac)₂·2H₂O、Cd(Ac)₂·2H₂The molar ratio of O to thioacetamide is 1:0.8-1.2: 1.8-3.0.

3. The MoSe of claim 1₂The preparation method of/ZnCdS nano-particles is characterized in that the product obtained in the step (1) is Zn_0.5Cd_0.5And (3) S nanoparticles.

4. The MoSe of claim 1₂A preparation method of ZnCdS nano-particles is characterized in that,

in step (2), NaBH₄The mass ratio of the Se powder to the sodium molybdate is 1:0.8-1.2: 1.3-2.

5. The MoSe of claim 1₂A preparation method of ZnCdS nano-particles is characterized in that,

in the step (3), ZnCdS nano-particles and MoSe₂The mass ratio of the nano-sheets is 88-97: 3-12.

6. The MoSe of claim 1₂The preparation method of the/ZnCdS nano-particles is characterized in that the hydrothermal reaction temperature in the step (1) or the step (2) is 180 ℃, and the hydrothermal reaction time is 20 hours.

7. MoSe according to any of claims 1-6₂The application of the/ZnCdS composite material in photocatalytic hydrogen production.

8. Use according to claim 7, wherein the MoSe is obtained by maintaining the temperature of the reaction system at 5-8 ℃ by cooling the circulating water under irradiation with visible light₂the/ZnCdS composite material is dispersed in water, 8 mL of lactic acid is added, and hydrogen is produced under continuous stirring and visible light.